1. Field of the Invention
This invention relates to an apparatus for reducing barrel erosion in telescoped ammunition.
2. Prior Art
Cased telescoped ammunition is comprised of a propellant charge having an axial bore or cavity, a projectile housed entirely within the axial bore of the propellant charge and a primer positioned aft of the projectile. When a cased telescoped round of ammunition is loaded into the chamber of a gun, the projectile, being housed in a propellant charge, is not seated in the barrel of the gun as is the projectile of a round of conventional ammunition in a gun chamber. Upon initiation of the primer of the telescoped round, the projectile is forced forward into a barrel of the gun and becomes seated in the barrel.
High performance telescoped ammunition cartridges are available and capable of launching projectiles at very high speeds. The improved performance is attractive from an overall system effectiveness standpoint. However, the high performance is obtained by using high charge densities and high performance propellants. These factors expose the barrels of the telescoped ammunition weapon system to a thermal environment far above that experienced in current gun systems. The estimated increase in heat flux over conventional systems is about 25%. The high heat fluxes will tend to increase the rate of barrel wear and reduce the barrel life. It would be desirable to reduce the heating and wear rates in telescoped ammunition barrels. These are some of the problems this invention overcomes.
Reducing wear rates is taught with respect to standard cartridges having a different physical configuration than telescoped cartridges. For example, U.S. Pat. No. 3,209,689 to McLennan teaches a wear additive encircling the propellant charge. The ablative material is added to a conventional loose propellant charge round of ammunition. The additive is bonded to the cartridge case or loosely placed around the propellant charge. There is a cooling effect upon detonation as the heat from the burning propellant charge and from propellant gases decomposes a sleeve causing the formation of a boundary layer of cool inner gases which insulate the bore surface.
Other wear reducing disclosures relating to standard cartridges include the following. U.S. Pat. No. 4,098,193 issued to Schroeder describes a gas evolving sheath 3 disposed about the inner periphery of casings 7 and behind a projectile 9 as seen in FIG. 1 of the patent. U.S. Pat. No. 4,203,364 issued to Dobbs illustrates an ammunition cartridge having a liquid-filled capsule 34 which, upon firing, ruptures and the liquid flows around the projectile 26 to lubricate and cool the barrel. U.S. Pat. No. 4,334,477 issued to Axelrod et al uses a plastic film 16 which produces a cooling gas when the propellant ignites.